rapidhash
A family of extremely fast, high-quality, platform-independent hash functions optimized for different performance profiles.
What is rapidhash?
Rapidhash is a family of non-cryptographic hash functions designed for exceptional speed and high-quality output across different input sizes and computing platforms. It solves the need for fast, reliable hashing in performance-sensitive applications like hash tables, data processing, and embedded systems. The project offers three optimized variants—rapidhash, rapidhashMicro, and rapidhashNano—each targeting specific performance profiles while maintaining platform independence.
Systems programmers, embedded developers, and performance engineers working on hash tables, data structures, or applications requiring high-speed hashing without cryptographic guarantees.
Developers choose Rapidhash for its combination of extreme performance (over 70GB/s throughput), excellent statistical quality validated by SMHasher tests, and platform independence that works across x86-64 and ARM architectures without specialized instructions.
Overview
Very fast, high quality, platform-independent hashing algorithm.
Use Cases
Best For
- Implementing high-performance hash tables in systems programming
- Data processing pipelines requiring fast hashing of large datasets
- Embedded and mobile applications where code size matters
- Server and HPC applications sensitive to cache performance
- Cross-platform projects needing consistent hashing across architectures
- Replacing slower hash functions in existing codebases
Not Ideal For
- Applications requiring cryptographic security, such as password hashing or digital signatures
- Projects that depend on hardware-specific vectorized instructions (e.g., AVX-512) for peak hashing performance
- Environments with legacy compilers not supporting modern C++ features needed for optimal compilation
- Use cases where interoperability with established hash standards like MD5 or SHA-256 is mandatory
Pros & Cons
Pros
Achieves over 70GB/s throughput on Apple M4 CPUs and nanosecond-level latency for small inputs, as demonstrated in benchmark tables comparing it to xxh3.
Optimized for both AMD64 and AArch64 architectures without relying on machine-specific instructions, ensuring consistent speed across diverse hardware like M1 Pro, Ryzen, and Neoverse V2.
Passes all SMHasher and SMHasher3 tests with collision probabilities close to ideal, validated on datasets of up to 67 billion keys, as shown in the collision study results.
Offers three variants—rapidhash for general use, rapidhashMicro for cache-friendly HPC apps, and rapidhashNano for compact embedded systems—each optimized for specific performance profiles.
Cons
rapidhashNano is 'considerably slower for larger inputs' beyond 48 bytes, and rapidhashMicro is 15-20% slower for inputs above 1KB, requiring careful selection based on use case.
Achieving the advertised instruction counts (e.g., ~185 for rapidhash with Clang-18+) requires modern compilers; performance may degrade with older or less optimized compilers like some MSVC versions.
Compared to established hashes like xxHash, Rapidhash has fewer third-party bindings and community resources, though ports to Java, Rust, etc., are available but less battle-tested.
Frequently Asked Questions
Related Projects
stbstb single-file public domain libraries for C/C++
{fmt}A modern formatting library
xxHashExtremely fast non-cryptographic hash algorithm
single_file_libsList of single-file C/C++ libraries, with emphasis on clause-less licenses.
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